The present invention relates, in general, to integrated circuit devices and, more particularly, to refresh methods for emissive displays.
Displays, such as Liquid Crystal Displays (LCDs), often have drivers for selecting pixels located on two sides of the display. The two sided access allows the LCD to be scanned in a manner similar to the conventional Cathode Ray Tubes (CRTs) which provide pixel access starting from the upper left corner of the display and proceeding from left-to-right and from top-to-bottom. Using this scanning method, the data stored in a memory map for the display is sequentially addressed in a row-major manner such that byte zero is horizontally adjacent to byte one. Thus, the bytes of data in the memory array are arranged as a digital representation of the data as it is visually viewed on the display.
A conventional Liquid Crystal Display (LCD) allows software programming of the display data that is encoded in bytes and stored in the graphics memory such that the data is transferred to the display in accordance with a visual conception of the data. For instance, a display that is two-hundred and forty pixels wide may store the first thirty bytes in a line buffer. The data in the memory is parallel loaded to a shift register and serially shifted one data bit at a time to the line buffer at the display. The line buffer circuitry at the display reassembles the serially shifted data which represents the data for the first line of the display. The thirty bytes stored in the line buffer at the display are presented in parallel, thus affecting all the pixels for the first line. From the software programmers point of view, the pixels in byte zero and byte one are horizontally adjacent and visually adjacent and all fall on the same axis. The row-major memory stores the entire first line of data for the display in the first thirty bytes of the memory.
Unlike a conventional LCD that is supplied with data sequentially addressed from graphical memory locations in accordance with a row-major display, a Light Emitting Device (LED) display is typically supplied with data addressed from graphical memory location in accordance with a column-major display. Instead of displaying the entire first line of pixels as in the case of the LCD, the LED display illuminates pixels on a column basis by providing sourcing and sinking currents to diodes in the display.
Hence, it would be advantageous to store data in a graphics memory for row-major addressing by providing that binary data to a LED display using column-major addressing. It would also be advantageous for such a method and apparatus to support even and odd interdigitated displays as well as bi-level and gray scale.